It is useful to know the location of people or objects for several reasons. The location of people or objects allows another party to find lost people or objects, such as a child or expensive equipments. Location information can also be used as a piece of data in conjunction with other information. For example, knowledge about the location of a portable laptop computer combined with knowledge about the location of all the printers in a building can allow a system to automatically route a print job from the laptop computer to the nearest printer, thus saving time and aggravation. Additionally, the knowledge of who is in a particular room in a building can also allow a system to adjust the temperature or lighting of that room to the individual's preferences or route that person's telephone calls to the phone in that room. These applications are examples illustrating the utility of a system that allows the location of people or objects to be known.
Conventional location systems are generally based on one of two methods. In the first method, the amount of time is measured for a signal to travel from point A to point B, and then the distance between the two points A and B is calculated. In the second method, the conventional location systems calculate the distance between a transmitter and a receiver based on a received signal strength indication (RSSI). The RSSI is a function of distance and a path-loss factor:RSSI=1/d−f where d is distance and f is the factor.
While the second method is conceptually simpler than the first method, the second method requires a transmitter or object identifier that has a consistent radiation power characteristic. In the conventional location systems implementing the second method, the transmitter or object identifier employs a horizontal loop antenna. The horizontal loop antennas of the conventional location systems have a loop plane that is parallel to the surface of the object where the transmitter or object identifier is placed. If the transmitter or object identifier is placed on a conductive object, such as equipment with a metal cabinet, the radiated power drops significantly in the conventional location systems.